The invention pertains to a microfluidic flow cell with a dry substance arranged in a cavity inside the flow cell for interaction with a fluid present in the cavity.
Microfluidic flow cells, which are being used increasingly as “minilabs” for the analysis and/or synthesis of fluids, especially in the field of diagnostics, contain reactive substances in liquid and/or solid form, which are introduced into the flow cells during the production of the cells. To introduce a dry reagent, one of the assembly steps involves applying a reagent liquid, that is, a carrier liquid in which a reagent is dissolved or suspended and which is later to be dried, to the area intended to hold the dry reagent inside the flow cell, e.g., a channel or a chamber, while that area is still accessible. After that, the entire flow cell component, only part of which has been wetted with the reagent, is subjected to a drying process before the further assembly steps are carried out; this drying step is often associated with a heat treatment to accelerate the process, or it takes the form of a freeze-drying process to protect the reagents and ensure the stability and resuspendability properties. The disadvantage is that the component, the dimensions of which usually far exceed those of the area to be dried, takes up a great deal of space in a drying chamber. In addition, the drying treatment can impair this flow cell component itself, especially the sensitive components mounted on it. Above all, the dry substance which has formed can be subject to degradation during the course of the final assembly of the flow cell, in particular through contact with air, atmospheric humidity, and welding heat or through the influence of the adhesives used during assembly, which are used in many cases hermetically to seal the corresponding channel areas of a microfluidic flow cell. A method for introducing a dry substance into a flow cell as described above is explained in, for example, EP 2 198 964 B1.